Watch: spaces in command are not preserved

When invoking Watch with arguments which contain spaces, the arguments are not preserved. For example, this command works as expected in an rc session:

% printf '%s %s %s\n' 1 2 3
1 2 3

But when run through Watch:

Watch printf '%s %s %s\n' 1 2 3

We would expect the argument parsing rc does when invoking Watch to be preserved, however the first string is split again:

To avoid this, Watch will need to quote any arguments with whitespace so that they are parsed correctly by rc again.